diff --git a/src/cal-period.scm b/src/cal-period.scm
index 17ee4e0..2d8216b 100644
--- a/src/cal-period.scm
+++ b/src/cal-period.scm
@@ -96,7 +96,7 @@
  (define (sort-period-markers l)
    (sort l
 	 (lambda (a b)
-	   (month<? (cadr a) (cadr b)))))
+	   (cal-month<? (cadr a) (cadr b)))))
 
  ;; Converts list of start/stop markers to list of pairs of months -
  ;; periods. The markers are lists in the form (start/stop cal-month).
@@ -227,16 +227,16 @@
     (test-equal? sort-period-markers
 		 (sort-period-markers '((start (2023 1)) (stop (2022 10)) (start (2022 3))))
 		 '((start (2022 3)) (stop (2022 10)) (start (2023 1))))
-    (test-equal? period-markers->periods
-	         (period-markers->periods
+    (test-equal? period-markers->cal-periods
+	         (period-markers->cal-periods
 		  '((start (2022 3)) (stop (2022 10)) (start (2023 1)) (stop (2023 4))))
 		 '(#t
 		   (((2022 3) (2022 10) #f #f)
 		    ((2023 1) (2023 4) #f #f))
 		   ""
 		   -1))
-    (test-equal? period-markers->periods-open
-	         (period-markers->periods
+    (test-equal? period-markers->cal-periods-open
+	         (period-markers->cal-periods
 		  '((start (2022 3)) (stop (2022 10)) (start (2023 1)) (stop (2023 4)) (start (2023 5))))
 		 '(#t
 		   (((2022 3) (2022 10) #f #f)
@@ -244,42 +244,42 @@
 		    ((2023 5) #f #f #f))
 		   ""
 		   -1))
-    (test-eq? period-duration
-	      (period->duration '((2023 1) (2023 4) #f #f)) 3)
+    (test-eq? cal-period->duration
+	      (cal-period->duration '((2023 1) (2023 4) #f #f)) 3)
     (parameterize ((*current-month* (list 2023 4)))
-      (test-eq? period-duration
-		(period->duration '((2023 1) #f #f #f)) 3))
-    (test-eq? periods-duration
-	      (periods-duration '(((2022 3) (2022 10) #f #f)
+      (test-eq? cal-period->duration
+		(cal-period->duration '((2023 1) #f #f #f)) 3))
+    (test-eq? cal-periods-duration
+	      (cal-periods-duration '(((2022 3) (2022 10) #f #f)
 				  ((2023 1) (2023 4) #f #f)))
 	      10)
-    (test-true month-in-period?
-	       (month-in-period? '((2022 1) (2022 4) #f #f) '(2022 3)))
-    (test-false month-in-period?
-		(month-in-period? '((2022 1) (2022 4) #f #f) '(2022 5)))
-    (test-true month-in-periods?
-	       (month-in-periods? '(((2022 1) (2022 4) #f #f)
+    (test-true cal-month-in-period?
+	       (cal-month-in-period? '((2022 1) (2022 4) #f #f) '(2022 3)))
+    (test-false cal-month-in-period?
+		(cal-month-in-period? '((2022 1) (2022 4) #f #f) '(2022 5)))
+    (test-true cal-month-in-periods?
+	       (cal-month-in-periods? '(((2022 1) (2022 4) #f #f)
 				    ((2023 5) (2023 10) #f #f))
 				  '(2022 3)))
-    (test-true month-in-periods?
-	       (month-in-periods? '(((2022 1) (2022 4) #f #f)
+    (test-true cal-month-in-periods?
+	       (cal-month-in-periods? '(((2022 1) (2022 4) #f #f)
 				    ((2023 5) (2023 10) #f #f))
 				  '(2023 7)))
-    (test-false month-in-periods?
-		(month-in-periods? '(((2022 1) (2022 4) #f #f)
+    (test-false cal-month-in-periods?
+		(cal-month-in-periods? '(((2022 1) (2022 4) #f #f)
 				     ((2023 5) (2023 10) #f #f))
 				   '(2022 10)))
-    (test-equal? period->string
-		 (period->string '((2022 1) (2022 4) #f #f))
+    (test-equal? cal-period->string
+		 (cal-period->string '((2022 1) (2022 4) #f #f))
 		 "2022-01..2022-04")
-    (test-equal? periods->string
-	         (periods->string '(((2022 1) (2022 4) #f #f)
+    (test-equal? cal-periods->string
+	         (cal-periods->string '(((2022 1) (2022 4) #f #f)
 				    ((2022 12) (2023 2) #f #f)))
 		 "2022-01..2022-04, 2022-12..2023-02")
-    (test-false periods-match (periods-match '(((2022 1) (2022 4) #f #f)
+    (test-false cal-periods-match (cal-periods-match '(((2022 1) (2022 4) #f #f)
 					       ((2022 12) (2023 2) #f #f))
 					     '(2022 5)))
-    (test-equal? periods-match (periods-match '(((2022 1) (2022 4) #f #f)
+    (test-equal? cal-periods-match (cal-periods-match '(((2022 1) (2022 4) #f #f)
 						((2022 12) (2023 2) #f #f))
 					      '(2022 2))
 		 '((2022 1) (2022 4) #f #f))